Category Archives: Jones et al 1998

Plots of Gaspe and Polar Urals Data

Just as an experiment, I plotted up all the ring widths for the Gaspé and Polar Urals sites, with each core displaced a little. What I was thinking of the type of graph that you see in seismic surveys. The look is interesting, given how much weight is placed downstream on these data sets in […]

Polar Urals: Shiyatov’s Finnish Academy Article

I’ve written on a number of occasions on Briffa’s Polar Urals reconstruction, which is used in nearly every multiproxy reconstruction, no doubt because of its uniquely cold MWP. It’s one of the key series in Crowley and Lowery [2000] and Jones et al [1998]; it’s not as important in MBH98-99 (which is more or less […]

Tornetrask Regressions

Briffa’s Tornetrask temperature reconstruction is done by regression analysis. Previously I reported that Briffa purported to justify his upward adjustment of 20th century MXD chronology (and downward adjustment of MWP reconstruction) by a very slight improvement of R2 (going from 0.503 to 0.553 – see Clim. Dyn 1992). I’ve attempted to replicate these regression calculations […]

Polar Urals #4: “Heartrot Bias”?

There appear to be some important sampling differences between subfossil and modern (living) cores. Briffa et al [CD 1992, 114] provide the following caveat with respect to using the RCS method (global curve fitting) for Tornetrask: “In applying this [RCS] method, each individual tree ring series should ideally start with the innermost ring (preferably near […]

Polar Urals #3: Crossdating

The three cores which account for 1032 being the "coldest" year of the millennium are 862450, 862470 and 862030. One other core (862460) is dated to the late 10th and early 11th century and contributes to early 11th century "coldness". The placement of these 4 cores has to be interpreted from the ring width information […]

Polar Urals #2: Broken Core

The tree ring dataset for the critical Polar Urals site has gaps of up to 59 years, has cores with as many 7 breaks in them. The problems are so pervasive that COFECHA testing simply fails – an almost unprecented occurrence in a tree ring data set.

Polar Urals #1

The Polar Urals site is a staple of multi-proxy studies. The Briffa et al. [1995] version is used in Jones et al [1998], MBH98, MBH99, Briffa et al. [2001] and most recently Jones and Mann (2004). An earlier version by Graybill and Shiyatov was used in Bradley and Jones [1993], Hughes and Diaz [1994] and […]

"Modern Sample Bias", RCS and Briffa’s "Adjustment"

Briffa’s Ph.D. student, Thomas Melvin, discusses the important impact of “modern sample bias” on RCS chronologies, discussing Tornetrask and Finnish sites in detail.

Tornetrask #4: Confidence Intervals

In my post on Tornetrask showing the impact of the Briffa-Jones "adjustment", I didn’t comment on confidence intervals.

Tornetrask #3: A Truncated Diagram

The inquiry about the impact of alpha trees reminded me of a cute little diagram truncation by Briffa, Jones et al.


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